You're absolutely right bareges. This is what makes this error so puzzling. Yahoo accepts the emaul address, and the address is functioning for my brother fine. The only problem being experienced is through my Pocomail and my ISP....

saoir wrote:You're absolutely right bareges. This is what makes this error so puzzling. Yahoo accepts the emaul address, and the address is functioning for my brother fine. The only problem being experienced is through my Pocomail and my ISP....

You're sending from your Yahoo address to derek@thisdomain.com , but in the other case from derek@thisdomain.com.
Those are two different things. The first is incoming, the second is outgoing.
So it appears your pop3 works, but not your smtp.

Eric wrote:]You're sending from your Yahoo address to derek@thisdomain.com , but in the other case from derek@thisdomain.com.Those are two different things. The first is incoming, the second is outgoing.So it appears your pop3 works, but not your smtp.

Still looking however.

Sorry Eric... you didn't read it correctly. I am sending TO both of those addresses from my normal everyday server address while be ing able to send lots fo other emails perfectly normally.